1. Field of Invention
The present invention relates to an automatic temperature monitoring system, particularly, but not exclusively, for monitoring the temperature of commercial refrigeration equipment whereby to provide an indication or alarm when the temperature of an equipment exceeds predetermined low and high limits for a predetermined period of time so that products contained within the refrigeration equipment can be safeguarded.
It is pointed out that the automatic temperature monitoring system of the present invention can include a plurality of temperature sensing probes associated with a plurality of equipment requiring temperature monitoring, and is not necessarily restricted for use with refrigeration equipment.
2. Description of Prior Art
Automatic temperature monitoring systems are known but have various disadvantages which the present invention overcomes or substantially reduces. For example, many known monitoring systems occupy very large spaces and have a very high energy consumption rate. They also require a high voltage supply or cannot operate on a local DC battery in emergency situations. Also, many of these circuits emit false alarms during a defrost cycle when monitoring refrigeration equipment. Still further, known equipment is mostly used for detecting increase in temperatures and not the decrease in temperatures, and the probes utilized often decalibrate themselves after years. When the equipment being monitored is located far away from the control panel, it requires a long conductor, and this conductor usually affects the signal value and introduces a false alarm signal.
Also, with the prior art, the monitoring temperature range is very small and does not register the temperature that is continuously monitored by the probes. Also, many of the known equipment is not provided with memory circuits to permit the operator to visualize the temperature variations of the equipment being monitored. Known equipment is also very difficult to install and operate, and further difficult to disconnect during the servicing of the refrigeration equipment which is being monitored by the circuit. Also, with many of the known systems that need to be programmed, after a power failure has occurred, it is often necessary to reprogram the equipment. Still further, the programming parameters are often easily accessible by unauthorized personnel and are often tampered with.
Furthermore, known prior art equipment does not provide sufficient warning time to the operator to permit him to react in time for the necessary corrective action. Known equipment also displays temperatures in degrees Celsius only and does not maintain the memory during power failures. It has also been found that once an alarm is triggered, it is difficult to cut- out the alarm. It is also difficult to temporarily disconnect the system for routine servicing of the equipment being monitored, and there is a risk of not reactivating the monitored equipment.